Isuzu N-Series. Manual - part 920

Transmission Control System (Smoother) 7A-135

P0914 (Flash Code 57)

Circuit Description
The gear shift position sensor is used to detect the shift
side lever position feedback for the shift solenoid valves
on the transmission gearshift control box and it is
installed to the transmission gearshift control box
assembly. The transmission control module (TCM) uses
the gear shift position sensor to determine the current
gear position with a combination of the gear select
position sensor. The gear shift position sensor has
following circuits.

• 5 volts reference circuit
• Low reference circuit
• Gear shift position sensor signal circuit

The TCM supplies 5 volts to the gear shift position
sensor on the 5 volts reference circuit. The TCM also
provides a ground on the low reference circuit. The gear
shift position sensor provides a signal to the TCM on the
gear shift position sensor signal circuit, which is relative
to the position changes of the select side. The TCM
monitors the gear shift position sensor signal for
voltages outside the normal range of the gear shift
position sensor. If the ECM detects an excessively low
or high gear shift position sensor voltage, this DTC will
set.
Condition for Running the DTC

• The ignition switch is ON.
• The ignition voltage is more than 20 volts.
• The emergency switch is OFF.

Condition for Setting the DTC

• The TCM detects that the gear shift position sensor

signal voltage is less than 0.5 volts or more than
4.5 volts.

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM inhibits gearshift control and holds gear

position when the diagnostic runs and fails.

• The TCM inhibits gear select & shift position

learning and half-clutch learning.

Condition for Clearing the DTC

• The TCM turns OFF the transmission warning

lamp when the diagnostic runs and does not fail.

• A current DTC clears when the diagnostic runs and

does not fail.

• A history DTC clears with the Tech 2 or reset

switch operation.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

• Ensure the sensor is tight and the sensor shaft are

not damaged.

Notice:

• If this DTC is present, engine will not crank except

applying the brake pedal or parking brake.

DTC P0914 (Flash Code 57)

Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or Transmission Control
Module (TCM) Connector End Views

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check -
Transmission Controls?

—

Go to Step 2

Go to Diagnostic

System Check -

Transmission

Controls

1. Install the Tech 2.
2. Turn OFF the ignition for 30 seconds.
3. Lift the driving wheels or drive the vehicle.
4. Let the vehicle run while observing the Gear

Shift Position Sensor parameter with the Tech
2.

Is the Gear Shift Position Sensor parameter within
the specified valve?

0.6 - 4.4 volts

Go to Diagnostic

Aids

Go to Step 3

Is the Gear Shift Position Sensor parameter less
than the specified value at Step 2?

0.5 volts

Go to Step 7

Go to Step 4

7A-136 Transmission Control System (Smoother)

1. Turn OFF the ignition.
2. Disconnect the gear shift position sensor

harness connector.

3. Turn ON the ignition, with the engine OFF.
4. Observe the Gear Shift Position Sensor

parameter with the Tech 2.

Is the Gear Shift Position Sensor parameter less
than the specified value?

0.5 volts

Go to Step 5

Go to Step 9

1. Turn OFF the ignition.
2. Connect a DMM between the 5 volts reference

circuit of the gear shift position sensor harness
(pin 1 of J-142 connector) and a known good
ground.

3. Turn ON the ignition, with the engine OFF.

Is the DMM voltage less than the specified value?

5.5 volts

Go to Step 6

Go to Step 10

1. Turn OFF the ignition.
2. Connect a test lamp between the low

reference circuit of the gear shift position
sensor harness (pin 3 of J-142 connector) and
battery voltage.

3. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 14

Go to Step 11

1. Turn OFF the ignition.
2. Disconnect the gear shift position sensor

harness connector.

3. Connect a DMM between the 5 volts reference

circuit of the gear select position sensor
harness (pin 1 of J-142 connector) and a
known good ground.

4. Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified value?

4.5 volts

Go to Step 8

Go to Step 12

1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between

the 5 volts reference circuit and the signal
circuit of the gear shift position sensor harness
(pin 1 and 2 of J-142 connector).

3. Turn ON the ignition, with the engine OFF.
4. Observe the Gear Shift Position Sensor

parameter with the Tech 2.

Is the Gear Shift Position Sensor parameter more
than the specified value?

4.5 volts

Go to Step 14

Go to Step 13

Important:
The gear shift position sensor may be damaged if
the sensor signal circuit is shorted to a voltage
source.

1. Test the signal circuit between the

transmission control module (TCM) (pin 19 of
B-426 connector) and the gear shift position
sensor (pin 2 of J-142 connector) for the
following conditions:

• A short to battery or ignition voltage
• A short to any 5 volts reference

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 18

Step

Action

Value(s)

Yes

Transmission Control System (Smoother) 7A-137

1. Test the 5 volts reference circuit between the

TCM (pin 18 of B-426 connector) and the gear
shift position sensor (pin 1 of J-142 connector)
for a short to battery or ignition voltage.

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 18

1. Test the low reference circuit between the

TCM (pin 20 of B-426 connector) and the gear
shift position sensor (pin 3 of J-142 connector)
for an open circuit or high resistance.

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 15

1. Test the 5 volts reference circuit between the

TCM (pin 18 of B-426 connector) and the gear
shift position sensor (pin 1 of J-142 connector)
for the following conditions:

• An open circuit
• A short to ground
• A short to the low reference circuit
• High resistance

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 15

1. Test the signal circuit between the TCM (pin

19 of B-426 connector) and the gear shift
position sensor (pin 2 of J-142 connector) for
the following conditions:

• An open circuit
• A short to ground
• A short to the low reference circuit
• High resistance

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 15

1. Turn OFF the ignition.
2. Disconnect the gear shift position sensor

harness connector.

3. Inspect for an intermittent and for poor

connections at the harness connector of the
gear shift position sensor (pins 1, 2 and 3 of J-
142 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 16

1. Turn OFF the ignition.
2. Disconnect the TCM harness connector.
3. Inspect for an intermittent and for poor

connections on the gear shift position sensor
circuits at the harness connector of the TCM
(pins 18, 19 and 20 of B-426 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 18

Step

Action

Value(s)

Yes

7A-138 Transmission Control System (Smoother)

1. Remove the gear shift position sensor. Refer

to Gear Shift Position Sensor Replacement in
this section.

2. Visually inspect the gear shift position sensor

for the following conditions:

• Physical damage
• Loose or improper installation

3. Visually inspect the lever shaft for damage that

connects to the gear select position sensor
shaft.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 17

Important:
Replacement gear shift position sensor must be
relearned.
Replace the gear shift position sensor. Refer to
Gear Shift Position Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 19

—

Important:
Replacement TCM must be programmed and
learned.
Replace the TCM. Refer to Transmission Control
Module (TCM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 19

—

1. Reconnect all previously disconnected

harness connector(s).

2. Clear the DTCs with the Tech 2.
3. Turn OFF the ignition for 30 seconds.
4. Lift the driving wheels or drive the vehicle.
5. Let the vehicle run.
6. Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 20

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic

Trouble Code (DTC)

List

System OK

Step

Action

Value(s)

Yes

Content .. 918 919 920 921 ..